1. Field of the Invention
The present invention relates generally to methods of efficiently recovering and reproducing substrates and methods of efficiently producing semiconductor wafers. More specifically, the present invention relates to methods of recovering and reproducing a first substrate having a semiconductor layer formed thereon and methods of producing semiconductor wafers including the steps of sticking a second substrate on the semiconductor layer and separating the first substrate from the semiconductor layer.
2. Description of the Background Art
To grow a group III nitride semiconductor such as AlxGayIn1-x-yN, wherein 0≦x, 0≦y, and x+y≦1, a sapphire substrate is currently, generally used (see Group III Nitride Semiconductor, edited by Isamu Akasaki, Kabushiki Kaisha Baifukan, Dec. 8, 1999, pp. 93-102, or Naoki Shibata, “Fabrication of LED Based on III-V Nitride and its Applications”, Journal of the Japanese Association for Crystal Growth, JACG, vol. 29, No. 3, 2002, pp. 283-287). A sapphire crystal and a group III nitride crystal, however, do not match in lattice constant, and to use a sapphire substrate to epitaxially grow a group III nitride semiconductor layer it is necessary to initially deposit a group III amorphous layer on the sapphire substrate as a low-temperature deposited buffer layer and subsequently deposit the group III nitride semiconductor layer on the buffer layer, which results in reduced production efficiency.
If the above substrate is a group III nitride substrate, then the group III nitride semiconductor layer can epitaxially grown directly on the group III nitride substrate. (See S. Porowski et al., “Thermodynamical properties of III-V nitrides and crystal growth of GaN at high N2 pressure”, Journal of Crystal Growth 178, Elsevier Science B. V., 1997, pp. 174-188). The group III nitride substrate, however, is difficult to grow in liquid phase, and accordingly need to be grown in vapor phase. This cannot provide a large bulk crystal and is significantly costly.